Oceania dwarfs Tanzania: about 8,600,000 km² km² against 945,781 km² km². At true size Oceania is about 9.1× larger — the whole of Tanzania fits into Oceania roughly 9 times.
The old Mercator map treated both about equally (1× vs 1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Tanzania fits 9× into Oceania.